1. Field of the Invention
The present invention relates in general to a method of producing a skin-covered pad of a seat, and more particularly to a method of producing a skin-covered pad which has decorative ridges or projections formed on a front face thereof.
2. Description of the Prior Art
Hitherto, in the field of seat manufacturing, a so-called "skin-covered pad" has been widely used as a cushion member of a seat cushion and/or a seatback. The skin-covered pad is arranged on the seat structure with its front face exposed to the outside. Usually, the skin-covered pad is produced by pouring a liquid material for foamed polyurethane or the like into a bag-shaped outer skin member held in a mold, and thereafter, curing the same in a suitable condition.
In order to improve the sitting comfort and the external appearance, some of the skin-covered pads are provided at their front faces with a plurality of decorative ridges or projections.
One of the methods for producing such ridges is taught by Japanese Patent First Provisional Publication No. 60-160990. In this method, the decorative ridges are previously provided to the bag-shaped outer skin member before the skin member is subjected to the molding of the polyurethane foam. That is, the bag-shaped outer skin member with the ridges is put into a mold, and thereafter, a liquid material for foamed polyurethane is poured into the bag-shaped skin member held in the mold and cured in a known manner. In order to properly hold the skin member therein, the mold has at its cavity bottom a corresponding number of grooves or recesses for engagement with the ridges of the skin member.
However, providing the ridges to the skin member prior to the urethane molding increases the number of production steps of the skin-covered pad. Furthermore, proper positioning of the skin member to the mold is difficult or at least troublesome because of need of the proper engagement between the ridges of the skin member and the grooves of the mold. In fact, if the urethane molding is carried out with the ridges of the skin member mismatched with the corresponding grooves of the mold, an inferior product is inevitably produced.
Furthermore, in the above-mentioned method, a new mold becomes necessary each time design changing of the skin-covered pad is required. This causes increase in cost of products.